Electrical apparatus



Jan- \1959 T. TOGNOLA 7 2,870,376

ELECTRICAL APPARATUS Filed Sept. 30, 1955 INVENTOR. TULLIO TOGNOLA BY ATTORNEYS United States atent ELECTRICAL APPARATUS Tullio Tognola, Sidney, N. Y., assignor to Bendix Aviation Corporation, Sidney, N. Y., a corporation of Delaware Application September 30, 1955, Serial No. 537,679

13 Claims. (Cl. 315-59) This invention relates to electrical apparatus and more particularly to means in an electrical circuit for creating electrical spark or are discharges.

One of the objects of the present invention is to provide a novelly constructed spark gap device of a type adapted for use in the ignition systems of combustion will produce a spark with greater energy from a given source than any prior known devices of comparable size and weight and adapted for comparable uses.

Still another object is to provide a spark gap device which is novelly so constructed that with but slight modification the same may be adapted for either high or low voltage discharges which embody relatively high energy.

The above and further objects and novel features of the present invention will more fully appear from the following detail description when the same is read in connection with the accompanying drawing. It is to be expressly understood, however, that the drawing is for purposes of illustration onlyand is not intended as a definition of the limits of the invention.

In the drawing, the single figure is asectional side elevation view showing one form of spark gap device embodying the invention.

The single embodiment of the invention illustrated in the drawing, by way of example, is in the form of an igniter or spark plug adapted for use in the ignition system of an engine or the like to initiate combustion of fuel or other combustible charge. The invention is particularly adapted for use in the ignition systems for so-called jet or gas turbine type engines and more particularly for aircraft engines in which size and weight are of prime importance and wherein high energy sparks are required espectially at high altitudes.

The novel structure contemplated by the present invention is designed to create a longer and, hence, a higher energy spark from a given source of energy than it has been possible to create with prior known devices under similar circumstances and conditions. The illustrated embodiment comprises a tubular metallic shell having an internal flange 11 which may serve as a ground electrode.

An insulating sleeve 12 is slidably received in shell 10 and rests on flange 11. At its end adjacent flange 11, said sleeve has an enlarged bore or recess 14, the diameter of which is somewhat greater than the diameter of the central passage 15 in the flange. A center electrode 16 comprises a spindle 17 in the reduced bore of sleeve 12 and a head portion 18 that engages the shoulder in the inner end of recess 14. The distance between electrodes 11 and 18 is quite substantial and considerably greater than the gaps provided in known spark gap constructions for use with voltages available in engine ignition systems and the like. v y 7 In order to promote sparking between electrodes 11 and 18, there is interposed .therebetween an insulating ring 19, a metallic ring 20 and a second insulating ring 21. The inner diameters of rings 19,20 and 21 are preferably the same as the diameter of opening 15 and the center electrode is preferably provided with a tip 22 which extends into the bore of insulating ring 19. The distance between tip 22 and metal .ring 20 along the inner surface of ring 19 is determined by the voltage available" from the source to which the center electrode is connected.

For the purpose of initiating the eventualspark between electrodes 11 and .18, the ring 20 is connected to ground through a resistance 23 which is of suflicient magnitude that but an inappreciable amount of energy is dissipated in it. Depending upon the other elements of the circuit, resistance 23 may be of the order of 5,000 to 100,000 ohms. The size of the resistance depends primarily upon the size of the storage condenser to which spindle .17. may be connected in a condenser discharge type of circu.it-the larger the condenser, the smaller the resistance. The latter should be just large enough to get the are or. spark started so a minimum of energy will be dissipated. in the resistance. It should be understood, however, that the values stated are not limiting values.

In operation, a voltage of sufficient magnitude to jump the .gap 22-20 is impressed across the electrodes and an arc will be initiated, thereby ionizing the gases within. the recess. This ionization reduces the resistance to arc- 1 ing to such an extent that the are or spark is caused to.

extend from electrodetip 22 to electrode 11 It is believed that the lengthening of the spark is also facilitated by the tendency of the spark to blow out of the confined space between the electrodes. The spark, once established, provides a path of less resistance than resistance 23 but of higher resistance than the shorter sparks of prior known devices. Hence, the sparks produced by the'presentde vice contain more energy than is contained in the spar-ksproduced by prior devices when energized by the same source at the same voltage. I If desired, the inner surface of ring 19 which-bridgesthe gap 22-20 may have a semi-conductive coating. The gap is thus converted into a so-called shunted-surface type gap across which a condenser discharge or steep wave front voltage will fire at relatively low voltage. The arc initiated across gap 2220 will elongate in the same manner as above described for high voltage operation. The inner surface of ring 21 may also be coated to form a semi-conductive bridge between ring 20 and electrode 11, but this is not necessary. It will be understood that electrode 11 may be connected to a terminalof the voltage source referred to above either through ground or through a return lead (not shown). Resistance 23 may also be connected directly to a terminal of the source as distinguished from being connected thereto through ground in the manner illustrated.

The electrode assembly may be held within the shell 10 in any suitable manner. One suitable means is shown in the form of ring 24 which may be secured in shell 10 by any known means, such as by screw threads, welding, soldering, press-fitting or the like.

There is thus provided a spark gap device or igniter of novel construction which functions in a novel manner to produce a longer and higher energy spark under given conditions than is possible in prior known devices under corresponding conditions. The device contemplated adapts itself to simple construction with a small number of parts in such a manner that full and etficieut use can be made of the heat energy generated by the sparks. The basic inventive concept lends itself to a variety of constructions, only one of which is illustrated in the drawings.

Although only a single embodiment of the invention is illustrated in the accompanying drawings and described in the foregoing specification, it is to be expressly understood that the invention is not limited thereto. For example, it is not essential that the center electrode spindle be fianged at 18 nor that the same be provided with tip 22 within insulating ring 19. If desired, the inner diameters of rings 19 and 21 may be somewhat greater than the corresponding diameters of annular electrodes 11 and 20. Also, the gap bridging insulating ring may be molded integrally with insulator 12 with the electrodes mounted therein as inserts. In some installations, it may be desirable to provide the spark path along the exterior peripheries of the electrodes and insulating rings 19 and 21. Various other changes may also be made, particularly in the design and arrangement of the parts illustrated, without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art.

What is claimed is:

l. A spark gap device comprising two spaced electrodes, a third electrode interposed between said two firstnamed electrodes and spaced in spark gap relation from each of them, and a resistance connected in circuit with said third electrode, said third electrode being annular and the spark gaps between said third electrode and each of said two first-named electrodes being in direct communication with each other through said third electrode.

2. A spark gap device as defined in claim 1 wherein said resistance is within the approximate range of about 5000 ohms to 100,000 ohms.

3. A spark gap device as defined in claim 1 wherein said resistance is of sufficient ohmage to cause the initiation of a spark discharge across the gap between said third electrode and one of said two first-named electrodes at the voltage impressed across said gap.

4. A spark gap device as defined in claim 1 wherein the gap between said third electrode and each of said two first-named electrodes is bridged by an insulator.

5. A spark gap device as defined in claim 4 wherein the gap bridging surface of at least one of said insulators is semi-conductive.

6. A spark gap device as defined in claim 4 wherein the active surfaces of said third electrode and one of said two first-named electrodes and the bridging surfaces of i said insulators are annular and form a recess in which the sparks between said electrodes occur.

7. A spark gap device as defined in claim 6 wherein one end of said recess is closed by the other of said two first-named electrodes and the other end of said recess is open.

8. A spark gap device comprising at least three electrodes in series spark gap relation, the intermediate one of said electrodes being in spark gap relation with each of the other two electrodes and one of the spark gaps thereby formed being in ionizing relation to the other gap thus formed, and a resistance connected in series circuit with said intermediate electrode.

9. A spark gap device as defined in claim 8 wherein said resistance is connected between said intermediate electrode and ground.

10. A spark gap device as defined in claim 8 wherein insulating means is interposed between and bridging said intermediate electrode and each of the other two of said electrodes and the sparking path between said electrodes is in a recess within said electrodes and insulating means.

11. A spark gap device as defined in claim 10 wherein said recess is closed at one end by one of said electrodes.

12. A spark gap device as defined in claim 10 wherein the surface of said insulating means bridging at least two of said electrodes within said recess is semi-conductive.

13. A spark gap device comprising a first annular electrode, a second annular electrode in spark gap relation with said first annular electrode, an input electrode in spark gap relation with said second annular electrode, means for insulating said electrodes from each other, said insulating means and said annular electrodes having coaxial openings therein to form a central passage therethrough, one end of said passage being closed by said input electrode to form a recess in which the arcing between the electrodes occurs, and a resistance connected in series circuit with said second annular electrode.

References Cited in the file of this patent UNITED STATES PATENTS 2,260,399 Peters et a1. Oct. 28, 1941 2,323,931 Peters July 13, 1943 2,572,209 Smits Oct. 23, 1951 2,573,473 Maschuch et al Oct. 30, 1951 

